PocketBook: Open links in the on-device web browser

Many PocketBook devices include a web browser, but when clicking a link
in KOReader, there was no option to open the link in the browser, there
was only an option to show a QR code (which can then be scanned by a
smartphone).

This commit implements `canOpenLink`/`openLink` on PocketBook using the
"browser.app", if available.

Tested on PB740 (InkPad 3).

Fixes: koreader#11782
Related: koreader#6597

frontend/device/pocketbook/device.lua

@@ -428,6 +428,27 @@ function PocketBook:setEventHandlers(uimgr)
     end
 end
 
+local function getBrowser()
+    if util.pathExists("/usr/bin/browser.app") then
+        return true, "/usr/bin/browser.app"
+    elseif util.pathExists("/ebrmain/bin/browser.app") then
+        return true, "/ebrmain/bin/browser.app"
+    end
+    return false
+end
+
+function PocketBook:canOpenLink()
+    return inkview.MultitaskingSupported() and getBrowser()
+end
+
+function PocketBook:openLink(link)
+    local found, bin = getBrowser()
+    if not found or not link or type(link) ~= "string" then return end
+
+    local argv = ffi.new("const char *[1]", {link})
+    inkview.OpenBook2(bin, 1, argv, 0)
+end
+
 -- Pocketbook HW rotation modes start from landsape, CCW
 local function landscape_ccw() return {
     1, 0, 3, 2,         -- PORTRAIT, LANDSCAPE, PORTRAIT_180, LANDSCAPE_180